Maybe Arnold Palmer said it best. These guys don't know what they're getting into.

The U.S. Open starts Thursday at Oakmont Country Club, with several apparent favorites — you've got your Tiger Woods, your Phil Mickelson, your Jim Furyk — but, really, it might be the most difficult major to handicap in years.

This is a record eighth U.S. Open at Oakmont, but it's also the first in 13 years, and only a dozen or so in the 156-golfer field have tournament experience on a course reputed to be the toughest in America. Consider this: Woods was an amateur when Ernie Els weathered five very hot days and a three-man playoff to win in 1994.

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This Oakmont doesn't look like that Oakmont, not with 5,000 trees leveled since then, the bunkers made deeper and more threatening and the Church Pews bunker expanded to make it the size of an airplane landing strip.

With so much trouble awaiting, and so little Oakmont experience out there, Palmer predicted it could be a very shaky opening round or two for many. He hasn't missed an Open at Oakmont in more than 50 years, but he almost sounded relieved to be sitting this one out.

For all the changes, he said, what sets Oakmont apart are greens so fast and tilted that the USGA is having trouble finding four adequate pin placements on each hole.

"I've talked to some of the guys that have been out there and I've talked to some of the former champions who have been out there, and they tell me this field — and this is just an observation — is not really ready for Oakmont," said Palmer, the tournament's honorary chairman. "That they haven't really learned yet how to play Oakmont."

Palmer is certain of that, if only because he has played Oakmont for 66 years and even The King isn't entirely sure if he fully knows a course whose greens are so wickedly fast, so unnervingly difficult to read.

"There are golf courses over the years that I could play a practice round or two and feel pretty comfortable that I knew how to play it," Palmer said. "Oakmont just doesn't happen to be that kind of golf course. I've played, well, since I was 12 years old. And I'm not even sure now that I know every shot that I should hit, if I could hit it."

Mickelson won The Players Championship last month and had a pair of third-place ties before that, and would seem to have plenty of momentum since switching to Butch Harmon as his coach. But even he won't know until he gets on the course how much his left wrist injury will affect him.

Mickelson played half a round Wednesday, and hasn't played a full round at Oakmont since injuring his wrist there chipping out of the thick rough last month.

Even if the wrist isn't a bother — he is resigned to playing in pain all week — there's the issue of his 72nd-hole collapse at Winged Foot last year, one that cost him his first U.S. Open title and his fourth major.

Woods, winner of four of the last nine majors, has owned the look of a champion all week, but skipped a final practice round Wednesday and limited himself to the driving range and putting green. Rory Sabbatini signed up to play with Woods, and asked him later why he didn't play.

"He said he stopped playing on Wednesday at the majors a couple of years ago, and it's worked out OK for him," Sabbatini said. "Hard to argue with that."

Another question is how a late-afternoon thunderstorm Wednesday that dumped nearly half an inch of rain on Oakmont will affect play. It could soften the greens enough to permit lower scoring than expected — remember, a similar rainstorm helped Johnny Miller shoot a final-round 63 and win the 1973 U.S. Open at Oakmont.

"It's not going to be what we planned for," said Tim Moraghan, the USGA agronomist. "Things were moving along quite well (before the storm). We thought we'd have a true, hard test for players on Thursday. The rain has altered this a little bit. We're going to try and do everything we can to get the golf course back to where it was before this little rain."

Or exactly what the field didn't want to hear. Sabbatini thinks Oakmont will be so difficult, he predicted the golfer who finishes last will be 40 over par — the equivalent of a bogey every other hole.

"These are the toughest greens we'll ever play in U.S. Open history, or even any other tournament for that matter," Els said before the rain storm. "With the rough and these greens, this is going to be a very, very tough test."

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